PROJECT SUMMARY Despite advances in the diagnosis and treatment of cardiovascular disease, the prevalence of heart failure continues to rise at epidemic rates. In response to varied injuries, the heart undergoes a complex process of remodeling, marked by upregulation of a fetal expression program and corresponding switching of metabolic activity to a fetal-like state, in close association with the development of cardiomyopathy. Over the course of the initial K08 funding period the Applicant trained in technical mass spectrometry based metabolomics and computational sciences, and their collective application to interrogate substrate utilization in cells in culture, metabolic measures of organ level physiology, and shifts in metabolic enzyme expression. Moreover, Applicant has applied these approaches to characterize the metabolic remodeling that occurs during the pathogenesis of heart failure, identifying previously unrecognized metabolic activities in the heart. These metabolic studies, however, have been limited to rodent models of myocardial injury, and it remains unclear to what extend these models recapitulate the development of human heart failure, particularly given critical differences in cardiac size, physiology, and bioenergetics between human and rodent cardiomyocytes. The development and advance of human induced pluripotent stem cells (iPSC) technologies has transformed the study of human disease. Human iPSCs may be readily differentiated into ventricular cardiomyocytes (iPSC-CMs) in vitro at high efficiencies and have been found to recapitulate in vivo human phenotypes across a number of genetic cardiomyopathies, with impaired calcium handling, decreased force generation, and re-expression of the metabolic fetal gene program. In this R03 proposal, the Applicant now aims to extend upon the initial K08 award, and apply comprehensive metabolomics to the study of human cardiomyopathy, in an effort to decipher the metabolic underpinnings of human heart failure. Using iPSC-CMs derived from patients with sequence- verified familial cardiomyopathies (dilated and hypertrophic cardiomyopathy) the Applicant will comprehensively define the metabolic changes that occur with cardiac pathology through state-of-the-art liquid chromatography - mass spectrometry. These proposed studies will shed tremendous insight into the metabolic basis for human cardiomyopathy, distinguish new metabolite biomarkers for impaired contractile activity, and identify metabolic pathways amenable to pharmacologic and dietary intervention, as well as will form the foundation for the Applicant's transition to an independent, R01 funded investigator.